1. Field of the Invention
The present invention relates to a spring-and-damper unit for installation between a vehicle body and a wheel guidance part of a motor vehicle. More specifically, the present invention relates to a spring and damper unit including a vibration damper and a spring, wherein the vibration damper has a piston rod having a piston which runs in a cylinder and divides the cylinder into a first working space surrounding the piston rod and a second working space remote from the piston rod. The vibration damper further includes a storage space arranged outside of the cylinder hydraulically connected to the second working space and serves as a compensation space for the piston rod volume moving into and out of the cylinder.
2. Description of the Related Art
A prior art vibration damper is disclosed in reference DE 42 33 701 A1. This reference discloses a storage device and/or compensation space arranged outside of a cylinder of the vibration damper and in which a gas space is separated from a fluid space in the interior of the storage space by a diaphragm. An embodiment with a second compensation space also exists. This type of vibration damper is designed to combine the advantages of a two-pipe vibration damper with those of a one-pipe vibration damper, to achieve a vibration damper with improved damping properties. However, the separating element between the gas space and the fluid space in the storage device is essential in this type of vibration damper to prevent the gas from going into solution in the damping fluid and to thus preclude the formation of a gas cushion in one working space. This is needed to ensure a correct response by the vibration damper even in the event of small strokes.
Another type of prior art vibration damper is disclosed, for example, in references DE 28 21 492 A1 and DE 28 55 561 A1. These spring-and-damper units include a spring or compensation space located outside of a cylinder of a vibration damper with a diaphragm between the gas filling and the damping fluid filling in the spring or compensation space. An embodiment with a spring space whose gas filling is separated from the damping fluid filling by a separating piston is also described. Such spring-and-damper units are used for the suspension and damping of the rear wheel in motorcycles and are installed between the rear wheel rocker arm and the frame so that the units do not have to absorb any wheel guidance forces.